Great importance is attached to the ultra-wideband technology, and the extensive research on ultra-wideband technology is carried out due to its advantages of high speed rate, low power consumption and the like. The current ultra-wideband system mainly has two realization systems, namely pulse system and carrier system, wherein the carrier-system ultra-wideband technology develops faster; and the technology standard based on MB-OFDM (Multi Band Orthogonal Frequency Division Multiplexing) scheme has already been established internationally, and various experimental chips and systems have been launched. In the current carrier system scheme, an ultra-wideband frequency spectrum is divided into a plurality of sub-frequency bands which are not overlapped with one another, data can only be sent on one sub-frequency band each time, in this way, the current spare frequency spectrum resources cannot be fully and flexibly used; moreover, a plurality of up-converters with different carrier frequencies are required, therefore the radio-frequency cost is increased; or a frequency synthesizer is used, but the time for switching between sub-frequency bands is increased. For the purpose of fully utilizing the frequency spectrum resources while suppressing the out-of-band radiation, a shaping filter with large stopband attenuation and very narrow transition bandwidth is required. But such filter has a very high order, thus not only the design difficulty and the system cost are increased, but also the system time delay is increased.